A disease of fowl adenovirus (FADV) infection is an infectious disease caused by group I poultry adenovirus. FADV belongs to the Family Adenoviridae, of which genome is composed of nonsegmented linear double-stranded DNA.
FADV has a spherical structure without envelope, of which the virus particles in the infected cell nucleus are often in a lattice-like arrangement, each virus particle contains a single linear double-strand DNA of 36 kb, two line-like strands of DNA and core protein form a core with a diameter of 60-65 nm, encapsulated within the capsid. The capsid is icosahedrally symmetrical and consists of 252 capsid particles with a diameter of 8-10 nm. The capsid particles are arranged on face of a triangle with 6 on each side, wherein 240 are hexon (non-apex capsid particles) and the other twelve were penton bases (apex capsid particles, Penton protein). Each penton base is combined with two fiber projections (Fiber-1 and Fiber-2 proteins) with a length of 9-77.5 nm.
In recent years, the morbidity of diseases caused by FADV has been suddenly increased, especially for broiler chickens which are 3-5 weeks old, and in severe cases the mortality rate could suddenly rise to above 80%.
Vaccination is effective in preventing the disease. However, in the prior art, it is difficult to obtain high-titer virus due to the difficulty of culturing the fowl adenovirus, in particular, the large differences between different isolated strains, resulting in the fact that it is usually difficult to provide an ideal immunization effect with the prepared vaccine and bio-safety risks can also caused by incomplete inactivation in whole virus vaccines. The antigenic components of subunit vaccines in the prior art are hexon (240/252), which constitute the major component of the viral capsid. However, the immunological efficacy has been always low and no product has been developed.
Therefore, clinically, there is an urgent need to develop a vaccine composition with a good immunological effect that can effectively prevent the epidemic of the disease.